In the past one system that allowed fracturing an interval included a series of external isolators such as open hole packers and a plurality of sliding sleeve valves. These valves could be operated with dropped balls of different sizes that would get progressively larger as sliding sleeve valves closer to the surface had to be operated by larger balls later in the procedure. Because of the size of the bottom hole assembly, there were only so many discrete ball sizes that could be used. The more zones that needed treatment in a given interval, the fewer the openings for treatment fluid that could be used in each zone. One example relevant to this concept is U.S. Pat. No. 7,591,312.
Some operators want a more even distribution of fracturing or acid treating fluids in each isolated zone in an interval. In the past one technique has been to install a plug, perforate the zone/section, and treat the zone just perforated. The next plug is installed to isolate the zone just treated and another gun is fired in the adjacent zone and the process is repeated until the entire interval is treated. At the end of the treatment all the plugs have to be milled out. The plugs are made from easily milled materials to expedite this process. This process is time consuming and therefore expensive and it generates a lot of cuttings that have to be removed from the borehole.
The present invention addresses an alternative technique to milling out all the plugs that were used to isolate intervals with an option to remove the plugs by making them disappear or by physically forcing them to hole bottom or grabbing them and removing them from the wellbore.
The concept of using tubular barriers in general that can disappear, usually with a chemical reaction, or by dissolving or using magnetic fields are illustrated in the following references: U.S. Pat. Nos. 6,568,470; 6,926,089 (FIGS. 4 and 5); U.S. Pat. Nos. 6,779,600; 6,145,593; 7,533,721; 7,493,956 and 5,425,424. Also of interest is US Publication 2005/0023004.
Those skilled in the art will better appreciate the details of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while appreciating that the full scope of the invention is to be found in the appended claims.